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Three Part Question

In [adult emergency department patients presenting with syncope] are [cardiac markers] worth measuring [to rule out myocardial infarction].

Clinical Scenario

A 78 year old male is brought to the Emergency Department having had a syncopal episode at home witnessed by his wife. He collapsed to the floor whilst standing, losing consciousness for 30 seconds and fully recovering within 5 minutes. He did not report chest pain or breathlessness. His presenting ECG shows no evidence of ischemia and he has no abnormalities on physical examination.
Should this gentleman have delayed cardiac markers measured in order to rule-out an acute myocardial infarction?

Search Strategy

1 SYNCOPE, VASOVAGAL/ or SYNCOPE/ or syncope.mp.
2 troponin.mp. or TROPONIN/ or TROPONIN T/ or TROPONIN I/ or myoglobin/
3 creatine kinase.mp. or Creatine Kinase/ or Isoenzymes/or Enzyme Tests/
4 2 or 3
5 1 and 4
6 myocardial infarct.mp. or Myocardial Infarction/
7 1 and 6
8 5 or 7
The search was applied via the OVID interface, to
1. MEDLINE 1966 to November Week 1 2005,
2. EMBASE 1980 to 2005 Week 45,
3. All Evidence Based Medicine Reviews (Cochrane Database of Systematic Reviews (CDSR), ACP journal club, Database of Abstracts of Reviews of Effects (DARE) and Cochrane Central Register of Controlled Trials (CCTR)).

Search Outcome

310 articles were identified by the literature search. The full texts of 23 abstracts thought to be relevant were obtained and read. Of these 23, 4 articles were thought to be of direct relevance and were included. Examination of the reference lists of the included articles revealed no other relevant articles.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Eagle KA, et al. 1983 USA	100 patients admitted to hospital with syncope.	Retrospective cohort study set in a General Medical ward and an Emergency Department.	Typical history of AMI with ECG changes and raised cardiac markers (CK & CK-MB).	74 underwent AMI 'rule-out'. 3 (4%) found to have AMI, all of whom died.	Retrospective. Random enrolment. Only two-thirds of patients had cardiac markers.
Link MS et al. 2001 USA	80 patients presenting to ED with syncope or near syncope who were admitted and underwent AMI 'rule-out'.	Retrospective cohort study set in Emergency Department.	Positive rule-in for AMI (ECG, CK and CK-MB).	1 out of 80 patients (1.3%) ruled in for AMI.	Retrospective. Only 80 out of 284 eligible patients enrolled. Those not admitted were not included.
Grossman SA et al. 2003 USA	141 patients over 65 admitted and having markers taken out of 319 patients presenting to ED with syncope.	Retrospective cohort study set in an Emergency Department.	Positive cardiac markers.	3 of 141 patients had raised markers (2.1%).	Retrospective. Study confined to elderly group. Only 62% had CK-MB and 5% Troponin I levels taken.
Hing R et al. 2005 Australia	113 patients presenting to the Emergency Department with syncope.	Prospective cohort study set in an Emergency Department.	Positive troponin T, cardiac cause for syncope and adverse cardiac outcome.	4 of 113 patients (3.5%) with positive troponin T. 3 (2.7%) of whom had adverse cardiac outcome.	Troponin T level taken as early as 4 hours after syncope in some cases. Due to the retrospective nature of the study this was not standardised and was at the discretion of the treating doctor. Only 113 out of 508 eligible patients were enrolled. 13 enrolled patients were lost to follow-up.

Comment(s)

There is very little research looking directly at the question and cardiac markers are not specifically mentioned in any current syncope guidelines. The evidence that is available suggests that the routine measurement of cardiac markers in adult patients presenting to the ED with syncope probably has a diagnostic yield for acute myocardial infarction of less than 1%. This may be slightly higher in very elderly patients who are more likely to present with atypical symptoms of acute myocardial infarction such as syncope. Even in this group, the number of patients who do not have other suggestive features of acute myocardial infarction such as characteristic ECG changes or a history of chest pain, is likely to be very small.

Clinical Bottom Line

There is little evidence to suggest that it is worth measuring cardiac markers in adult patients presenting to the ED with syncope in the absence of chest pain or ECG changes suggestive of acute myocardial infarction.

References

1. Eagle KA, Black HR. The impact of diagnostic tests in evaluating people with syncope. Yale Journal of Biology and Medicine 1983; 56(1): 1-8.
2. Link MS, Lauer EP, Homoud MK, et al. Low yield of rule-out myocardial infarction protocol in patients presenting with syncope. American Journal of Cardiology 2001; 88(6): 706-7.
3. Grossman SA, Van Epp S, Arnold R, et al. The value of cardiac enzymes in elderly patients presenting to the emergency department with syncope. Journals of Gerontology Series A-Biological Sciences & Medical Sciences 2003; 58(11): 1055-8.
4. Hing R, Harris R. Relative utility of serum troponin and the OESIL score in syncope. Emergency Medicine Australasia 2005; 17(1): 31-38.